1. Field of the Invention
One aspect of the invention relates to a signal bandwidth extending apparatus which converts a signal, such as speech, music, or audio with limited bandwidth, into a wideband signal.
2. Description of the Related Art
When the bandwidth of the signal (input signal) such as speech, music, or audio is extended to a wideband signal, in order for the sound to be heard not artificially but naturally, there is a need to properly change the signal processing method used for extending a frequency band so as it corresponds to the signal (target signal) of the bandwidth which is to be extended and is included in the input signals.
As a related bandwidth extension processing method, there are a scheme in which the frequency band is extended after performing a linear prediction analysis on the speech when the target signal is a speech, a scheme in which the frequency band is extended after performing a frequency domain transformation on the music or the audio when the target signal is music or audio, and a scheme in which the frequency band to be extended is switched based on whether or not the speech is a voiced sound or an unvoiced sound even when the target signal is a speech (see JP-A-002-82685, for instance).
In the related signal bandwidth extending apparatuses, since the bandwidth extension is performed over the entire section even when the target signal and other signals (non-target signals) than the target signal are mixed in the input signal, heavy computational load is needed.